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US 12,146,809 B2Granted
Method and apparatus for monitoring number density of aerosol particles
AssigneeDekati Oy
InventorsAnssi Arffman, Ari Ukkonen, Markus Nikka, Esa Luntta, Erkki Lamminen
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Abstract
An apparatus for measuring aerosol particles includes a charging unit to form charged particles by charging particles of an aerosol sample flow by diffusion charging, and a collecting unit to provide an electric current by collecting charges from the charged particles by diffusion of the charged particles, the electric current being indicative of number density of aerosol particles of the aerosol sample flow. The internal pressure of the collecting unit is maintained at a reduced value in order to provide a flat response of the electric current for detecting nanoparticles of different sizes.
Claims11
An apparatus for measuring aerosol particles, the apparatus comprising:
- a charging unit configured to form charged particles by charging particles of an aerosol sample flow by diffusion charging,
- a collecting unit configured to provide an electric current by collecting charges from the charged particles by diffusion of the charged particles, the electric current being indicative of a number density of aerosol particles of the aerosol sample flow,
- a pressure reducing unit configured to reduce pressure of the aerosol sample flow, and
- a suction unit configured to draw the aerosol sample flow via the charging unit to the collecting unit, wherein a charging efficiency function is indicative of an efficiency of the diffusion charging to charge the particles as a function of particle size,
- wherein a collecting efficiency function is indicative of an efficiency for collecting the charges by diffusion of the charged particles as a function of particle size,
- wherein the pressure reducing unit and the suction unit are arranged to keep an internal pressure of the collecting unit at a selected pressure value such that a negative slope of the collecting efficiency function at least partly compensates a positive slope of the charging efficiency function at least in the particle size range of 40 nm to 200 nm, the selected pressure value being smaller than or equal to 80 kPa,
- wherein the suction unit comprises a pump configured to draw a flow from the collecting unit and/or a valve configured to control a flow rate of the suction unit, wherein the suction unit comprises a pressure sensor configured to provide a signal indicative of the internal pressure of the collecting unit, and a control unit configured to adjust the flow rate of the suction unit, so as to keep the internal pressure of the collecting unit substantially equal to the selected pressure value,
- wherein the control unit is configured to provide a control signal for controlling operation of the valve and/or for controlling operation of the pump based on the signal of the pressure sensor.
5 more elements
A method for measuring aerosol particles, the method comprising:
- using a charging unit to form charged particles from particles of an aerosol sample flow by diffusion charging,
- using a pressure reducing unit to reduce pressure of the aerosol sample flow,
- using a suction unit to draw the aerosol sample flow via the charging unit to a collecting unit,
- using the collecting unit to provide an electric current by collecting charges from the charged particles, wherein the charges are collected from the charged particles by diffusion of the charged particles, the electric current being indicative of a number density of aerosol particles of the aerosol sample flow, and
- keeping an internal pressure of the collecting unit at a selected pressure value such that a negative slope of a collecting efficiency function at least partly compensates a positive slope of a charging efficiency function at least in the particle size range of 40 nm to 200 nm, wherein the charging efficiency function is indicative of an efficiency of the diffusion charging to charge the particles as a function of particle size, and wherein the collecting efficiency function is indicative of an efficiency for collecting the charges by diffusion of the charged particles as a function of particle, the selected pressure value being smaller than or equal to 80 kPa,
- wherein the suction unit comprises a pump configured to draw a flow from the collecting unit and/or a valve configured to control a flow rate of the suction unit,
- wherein the suction unit comprises a pressure sensor configured to provide a signal indicative of the internal pressure of the collecting unit, and a control unit configured to adjust the flow rate of the suction unit, so as to keep the internal pressure of the collecting unit substantially equal to the selected pressure value,
- wherein the control unit is configured to provide a control signal for controlling operation the valve and/or for controlling operation of the pump based on the signal of the pressure sensor.
5 more elements
Dependencies are inferred from the claim text.